Wellhead Lubricator Cover

ABSTRACT

In the area of oilfield wellhead equipment, and specifically the wellhead lubricator, there is often the problem of the fluid or gas inside the lubricator and/or wellhead freezing in cold winter climates. A wellhead lubricator cover is described which can be secured around the wellhead, thereby isolating the wellhead lubricator and preventing the fluid or gas inside the lubricator from freezing.

FIELD OF THE INVENTION

The present invention relates to oil and gas well operation and specifically to an apparatus to cover the gas/oil wellhead and prevent the wellhead lubricator fluid from freezing.

BACKGROUND OF THE INVENTION General Background

Oil and gas drilling has traditionally been a difficult and expensive undertaking. Merely reaching the oil, gas or other resource, many thousands of feet in the ground, is acknowledged as a tremendous feat of engineering. But sometimes equally difficult is coping with the often severe weather associated with the immediate drilling environment above ground during drilling operations and wellhead installations.

It appears that much of the oil, gas and other minerals to be found throughout the world happen to be in some of the lesser hospitable environments: the arctic, the desert, offshore and the like. High winds, tropical storms, low temperatures, and moisture are excessively prominent in many areas where drilling takes place.

Among the equipment and fittings usually found on the wellhead of an oil or gas well, there is a device called the “wellhead lubricator”. Wellhead lubricator is a term of art used in the oil and gas industry to describe a tool that is normally mounted on the top of a wellhead or “Christmas Tree” (another term of art in the industry) to house a wireline tool (another term of art in the industry) while the shutoff and/or master valve of the wellhead assembly are either opened to lower tools into the well under pressure or closed to prevent accidental falling of the wireline tool into the well during “make-up” or withdrawal. The lubricator acts as a pressure housing to allow a straight opening to the downhole tubing or to house a wireline tool during well shut-in.

The plunger lubricator attaches to the top of the wellhead tubing, it is installed when the well flow starts to decline. It acts as an access point to remove and inspect the wellhead plunger from the tubing. A wellhead plunger is a steel drift that is inserted in the wellhead tubing to lift liquid from the bottom of the well bore to keep the well from liquid loading (a term of art in the industry). Liquid accumulation in the well will drastically affect the productivity of the well in a negative manner.

If the wellhead lubricator is exposed to extremely cold temperatures, the fluids contained therein can freeze, causing the wellhead to cease functioning and valuable production to be lost. Additional expense must be incurred to have skilled technicians attend at the well site to remedy the freeze-off and restore flow from the well.

The present invention helps prevent freezing of the fluid in the wellhead lubricator, by insulating the fluid from cold temperatures. The present invention can be wrapped around the piping contained on the wellhead, and can be secured tightly around all sides of such piping through the use of Velcro fastening. This allows for the various gauges that may be present on the wellhead to remain exposed, while covering the wellhead lubricator.

Prior Art

Prior lubricator covers are generally less user friendly and less tear resistant. The most common covers used in the industry are made of plastic and therefore tear easily, and are less adaptable to differences in pipe heights. Further, such covers can often be opened only part way, and are secured with strings, buttons, or straps rather than Velcro, and therefore are more difficult to apply and remove.

There exists in the prior art several approaches to the prevention of wellhead freezing, often involving the application of known heat tracing methods. Canadian Patent No. 1,299,620, issued to Anderson on Apr. 29, 1992 (similar to U.S. Pat. No. 5,049,724, issued to Anderson on Sep. 17, 1991), describes a flexible, insulated jacket adapted to fit closely around a specific piece of wellhead equipment. Heat is delivered to the wellhead equipment by means of electric heating cables disposed in a selected pattern within the jacket, and connected to an external electrical power source. Although the Anderson apparatus may function adequately to prevent freezing of the equipment, it has significant disadvantages. Firstly, it must be custom-fabricated to suit particular equipment, and thus is not readily adaptable for effective or efficient use with other equipment. Secondly, it requires an external electrical power source, which may be practically unfeasible or prohibitively expensive, particularly at remote well sites, where the only practicable way of providing electrical power source might be by use of a generator requiring a reliable supply of refined fuel such as diesel oil.

U.S. Pat. No. 6,032,732, issued to Yewell on Mar. 7, 2000, discloses a wellhead heating system that circulates heated coolant, from a liquid-cooled engine driving an oil well pumper, through insulated conduit arranged as desired in thermal contact with the wellhead equipment, such that heat from the circulating coolant is transferred to the equipment. The Yewell apparatus has a serious drawback, however, in that it is applicable only at well sites where a source of heated fluid is readily available, such as where a liquid-cooled engine has been provided for one reason or another.

No existing patents were found in relation to the existing lubricator covers.

A list of other prior patents which may be of interest are cited below:

U.S. Pat. No. 4,489,780 issued to Gus A. Duhon discloses the apparatus of the wellhead lubricator.

U.S. Pat. No. 4,600,339 issued to Yvon Castel deals with a shield for protecting a well head and functional modules of an underwater station.

U.S. Pat. No. 6,776,227 issued to Rodney T. Beida pertains to a wellhead heating apparatus and method, utilizing radiant heat from a flameless heater to heat the lubricator fluid in a heat exchange

U.S. Pat. No. 5,026,219 issued to Henry Wallace discloses a wellhead and welder protector comprising of an easily erected, temporary shelter designed to envelope a wellhead and the immediate surrounding area.

U.S. Pat. Nos. 4,600,339, 5,026,219, and 6,776,227 are clearly distinguishable from the present invention. U.S. Pat. No. 4,600,339 deals with an underwater shield composed of plastic or treated wood that is rested on a metal sheet, acting as a cage around the wellhead operator. U.S. Pat. No. 6,776,227 involves a flameless heater to heat fluid and pump it through a conduit loop, such that the heat from the fluid is transferred to the equipment, maintaining it at sufficient temperature to prevent freeze-off U.S. Pat. No. 5,026,219 involves a tent-like structure rather than a cover that directly attaches to the wellhead.

Thus, based upon the above and foregoing, one can ascertain that there clearly exists a need for an easily applied/removed wellhead protective cover, which would allow for more efficient insulation of wellheads, to prevent freezing without the need of heat and/or an external power source.

SUMMARY OF THE INVENTION

The present invention overcomes these prior art problems by providing a user-friendly, adjustable wellhead protection system, which is highly reliable, easy to apply, and very cost effective.

The preferred embodiment of the invention includes the combination of inner thermal insulating and outer waterproofing shell.

The preferred embodiment of the shell is a waterproof, breathable fabric, such as GORE-TEX (a trademark of the W. L. Gore & Associates, Inc.) or the like, that is tear resistant and chemical resistant. A suitable fabric of this type is disclosed in U.S. Pat. No. 4,443,511, issued Apr. 17, 1984, and often referred to as STRETCH GORE-TEX. This is, as described in the patent, a Lycra (E. I. DuPont de Nemours and Company) fabric covered with a GORE-TEX membrane having stretch capability.

This preferred embodiment contains Velcro strips along the edges, allowing the cover to be easily secured to the gas/oil wellhead. In this respect, it is preferred to use complimentary fasteners of the type sold under the trademark “VELCRO” by Velcro Corp. Even with the prior designs which are somewhat adjustable to the differing types and sizes of pipes, the adjustment mechanism is difficult to use, especially under cold temperatures and limited visibility. Velcro is superior in this regard because it is easily adjusted to fit varying sizes and types of pipes and gauges.

This embodiment is designed to slide over the top of the wellhead, and fasten using the Velcro strips along that are located along the edges of the apparatus.

It is also an object of the present invention to provide insulation of the wellhead lubricator in cold weather, and reduce the chance of the lubricator fluid freezing, which would normally prohibit such activities.

It is also an object of the present invention to provide a wellhead lubricator cover which is relatively light in weight, easily transportable and quickly attached to the wellhead, yet heavy duty and able to withstand cold weather environments.

DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature and objects of the present invention, reference should be had to the following detailed description, taken in conjunction with the accompanying drawings, in which like parts are given like reference numerals, and wherein:

FIG. 1 is a side view of a typical wellhead as found in the oil/gas industry.

FIG. 2 is a side view of a wellhead, with the preferred embodiment of the wellhead protector affixed.

FIG. 3 is a front elevational view of the preferred embodiment of the invention, the outer shell being closed for purposes of illustration;

FIG. 4 is a side elevational view of the preferred embodiment of the invention, the outer shell being opened for purposes of illustration.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to the oil/gas industry, and more specifically the area of oilfield wellheads.

Referring to FIG. 1, a wellhead is a general term used to describe the component at the surface of an oil or gas well that provides the structural and pressure-containing interface for the drilling and production equipment. The primary purpose of a wellhead is to provide the suspension point and pressure seals for the casing/tubing strings 5 that run from the bottom of the hole sections to the surface pressure control equipment and plunger lubricator 1.

While drilling the gas/oil well, surface pressure control is provided by a blowout preventer, or BOP (terms of art in the industry). If the pressure is not contained during drilling operations by the column of drilling fluid, casings, wellhead, and BOP, a well blowout could occur. The BOP is the base of the wellhead, and is used to keep the wellhead tubing 3 and wellhead casing 5 in the ground while drilling, in case there is a kick of pressure or “blowout” (a term of art in the industry) while drilling.

Once the well has been drilled, it is completed to provide an interface with the reservoir rock and a tubular conduit for the well fluids. The surface pressure control is provided by the “Christmas tree” (a term of art in the industry), which is installed on top of the wellhead, with wellhead isolation valves 4 and choke equipment to control the flow of well fluids and gas during production.

Freezing of wellhead equipment is a common risk for oil wells and gas wells in regions that experience extremely cold winters, such as Alaska and northern Canada. Natural gas contains hydrates, which may condense out of the gas and then solidify when temperatures are very low, particularly when the situation is aggravated by a drop in gas pressure. Referring to FIG. 1, gas or oil flows through the wellhead tubing 3, then through the plunger lubricator 1, and onward through the hi-line piping 2 into a separator building wherein the gas and liquids are separated and metered. However, freezing can occur while flowing through the wellhead tubing and plunger lubricator, causing major issues in the separation process.

Unless sufficient heat is provided, or unless other means are provided for preventing condensation of hydrates, the wellhead equipment installed on a producing well to control and regulate flow of oil or gas, as the case may be, can “freeze off” and cease to function when temperatures fall below freezing (i.e., zero degrees Celsius). When this happens, valuable production is lost, and additional expense must be incurred to have skilled technicians attend at the well site to remedy the freeze-off and restore flow from the well.

Other approaches to the problem of freezing have included provision of heat tracing loops circulating hot water or steam from heaters or boilers, or direct injection of antifreeze fluids such as methanol. Such approaches are excessively expensive if not entirely impractical for remote well sites, because of the cost and inconvenience of maintaining a reliable source of power or fuel for the heaters or boilers, or providing injection pumps and sufficient supplies of antifreeze fluids. In fact, well-operating companies may find it less costly overall to incur occasional production losses from wellhead freeze-off at remote well locations, plus the expense of sending technicians out to remedy freeze-off situations, than to provide means for keeping the remote wellheads warm, given the cost of providing heat sources (e.g., electric power, diesel generators, or propane heaters) or antifreeze injection equipment needed to prevent freeze-off.

It is commonly necessary to provide an enclosure in the general vicinity of a wellhead to house accessory equipment, such as meters or compressors, which must be maintained above particular temperatures in order to remain functional. The enclosures are often heated using flameless infrared catalytic heaters. Such heaters may be fuelled by propane, although that requires provision of a suitable source of propane at or near the well site. More conveniently and more economically, it is often feasible to fuel these heaters with natural gas diverted directly from the well.

Whether fuelled by natural gas or other fuels, however, such heaters are not always used as effectively or efficiently as possible. A heater in a given equipment enclosure will commonly generate more heat than needed to keep the equipment in the enclosure at the desired temperature.

For the foregoing reasons, there is a need in the oil and gas industry for an apparatus for preventing freezing of wellhead equipment associated with gas wells and oil wells, without the use of heat and external power. In particular, there is a need for such apparatus and methods that minimize or eliminate the need for antifreeze injection, or for supplementary power or fuel. The present invention is directed to these needs.

The present invention enables workers in the oilfield to easily attach an apparatus to the wellhead that will help keep the wellhead lubricator fluid from freezing. The apparatus can be applied in a matter of seconds, and more importantly, can be adapted to fit differing sizes and types of wellheads. No heat or electricity is needed in the present embodiment.

The preferred embodiment of the invention includes the combination of inner thermal insulating and outer waterproofing shell. Referring to FIG. 3 and FIG. 4, the main body of the apparatus is shown at 8, and the Velcro straps shown at 9.

This preferred embodiment of the present invention consists of a waterproof, breathable material, such as GORE-TEX® or the like, that is tear resistant and chemical resistant. A suitable fabric of this type is disclosed in U.S. Pat. No. 4,443,511, issued Apr. 17, 1984, and often referred to as STRETCH GORE-TEX. This is, as described in the patent, a Lycra (E. I. DuPont de Nemours and Company) fabric covered with a GORE-TEX membrane having stretch capability.

The fabric is filled with insulation, to assist in the retention of heat and exclusion of cold temperatures from the wellhead lubricator.

This preferred embodiment contains Velcro strips along the edges, allowing the cover to be easily secured to the gas/oil wellhead. Even with the prior designs which are somewhat adjustable to the differing types and sizes of pipes, the adjustment mechanism is difficult to use, especially under cold temperatures and limited visibility. Velcro is superior in this regard because it is easily adjusted to fit varying sizes and types of pipes and gauges.

Referring to FIG. 2, the apparatus can be slipped over the plunger lubricator 1 and secured using the Velcro strips. The apparatus covers the chemical injection point 6, thereby sealing the lubricator from the elements. The apparatus also covers the wellhead tubing 3, thereby protecting the gas or oil flowing inside the wellhead tubing from freezing.

The apparatus helps keep the temperature of the fluid or gas flowing throughout the wellhead from falling below freezing (i.e., zero degrees Celsius). 

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
 1. An apparatus for use in association with an oilfield wellhead, said apparatus comprising of: an inner thermal insulating and outer waterproofing shell (a suitable fabric of this type is disclosed in U.S. Pat. No. 4,443,511, issued Apr. 17, 1984, and often referred to as STRETCH GORE-TEX); and Velcro strips along the edges, allowing the apparatus to be easily secured to the gas/oil wellhead (a suitable fastener of this type is sold under the trademark “VELCRO” by Velcro Corp).
 2. An apparatus under claim 1 that is able to adjust to different types and sizes of wellheads, and be attached to said wellhead to prevent freezing of the fluid or gas contained in the wellhead lubricator.
 3. An apparatus under claim 1 that is light in weight, easily transportable and quickly attached to the wellhead, yet sufficiently heavy duty to withstand cold weather environments. 